Repeal the individual mandate, the employer mandate and end the subsidy to the federal exchange. Let nature take its course.
The individual and employer mandates weren’t the worst problem - it was the massive regulations on the type of policies that could even be offered, what they had to cover, etc.
Now I’m not discounting the constitutional problem with the mandate - talking strictly the logistics of how it eliminated the very existence of good, inexpensive plans and healthcare providers. The mandates could have been in place without any of that happening.